AFR control & monitoring

[billjam]

I know, there's a zillion threads here about this stuff - and to a newbie, that's the problem. Its hard to cut through the jargon, the side issues and the hi-jacked threads to really get a clear picture of what a BASIC setup should be for setting up and monitoring AFRs.
In itself, that is a real can of worms because everyone is looking for something different, has different budgets and/or different levels of expertise, but I think my situation could be reasonably typical of a large number of 930 daily drivers who have "played" with their engine a little and do 99% of their driving on the road.
After I get it setup, all I really want to do is to be able to monitor my AFR and boost for peace of mind.

First of all, this is what we are working with ...
1986 930, US spec (930/68), everything stock except:

• SC cams
• K27 7200 turbo
• B&B muffler
• mildly ported and polished heads
• B6 intercooler (1/2 bay)
• no air pump, plugged air injection ports
• no cat
• adjustable WUR (on order)
• RPM solenoid valve (on order)
• manual boost controller (planned)

To this list, I am planning to add an Innovate boost gauge and one of their AFR gauge kits (DB, LC-1 or XD-16) to enable me to do basic setup for the RPM solenoid valve as well as ongoing monitoring of the AFR.

When I sat down to write this, my question was going to be ...
Can I put this in the parts box for for the next owner?

That question still applies.
I don't really know that the O2 sensor does much any more now that the air pump and cat have been removed. I'd also like to use this port for the Innovate AFR sensor (if threads are the same).

I don't want to spend the other half of my house on this or make the car too complicated to setup so I am looking for confirmation that what I am planning (adj WUR, RPM solenoid and gauges) is a practical and cost effective way of giving me the means to setup and monitor boost and AFRs.

Oh yes, and can I ditch the O2 sensor?

Bill

[rsrmike]

Hello, you are on the right track w/ innovate products. You cannot use that oxygen sensor port for a wide band sensor as it is before the turbo.

The old style "narrow band" sensors worked different from the new "wide band". The wide band cannot be exposed to the heat and pressure in the exhaust before the turbo. It will be innacurate and quickly destroyed if placed there.

You need to install a bung in the exhaust some where close to 3-4 inches AFTER the turbine outlet.

I can't give you much advice on your WUR but I would recommend investing in a fuel pressure gauge to monitor control pressure, as well as an ambient thermometer(for cold start notes), and a log book to make notes on all you adjustments, and resulting AFR changes.

Good luck!

[billjam]

I'm still looking confirmation that my O2 sensor is redundant .

If a wide band sensor for Innovate AFR gauge needs to go after the turbo, I have about 5" of pipe before the muffler so I guess that's where it will have to go. I recall reading somewhere that they should also go in top half of pipe as well.
I currently have engine apart and its a bit hard to visualize how I would access this sensor once it is back in the car. From memory, there's no easy way to get at this location from above or below. Would it be a partial engine drop for access to the sensor?
Can someone with a sensor in this area chime in and advise how they did it?

[rsrmike]

Your factory O2 sensor is not needed for your application.

It's only function is to provide rich/lean "switch point" info to lambda valve.

The lambda valve's function slightly alters the AFR from rich/lean for optimum Catalyst efficiency. It simply runs at a fixed value w/ o2 sensor unplugged. 50% duty cyle?? comes to mind. It alters the AFR much like the WUR. By modifying control pressure. Higher duty cycle=lower control pressure=richer AFR. Since you don't have a cat, you can remove it. It's only adding a potential variable and failure point to your system. Your WUR will have to be adjusted accordingly, to get your control pressure back down to where it was with functioning lamda valve.

You are correct in sensor placement, it just needs to be at a downward angle. Moisture from exhaust condensation will collect in the sensor and fry the heater circuit.

You will most likely need to trim the engine sheet metal to make it fit in the correct postion. You are in a unique position w/ engine dismantled. I would suggest experimenting w/ a small removable access plate, sectioned in to the rear sheet metal, that would allow serving the sensor from the top of the engine compartment. There are O2 sensor wrenches that accept a 3/8 " extension that would make it easy to remove if that were the case. It would be a handy place to run the wiring harness from the sensor into the engine compartment, as they never seem quite long enough to run the exact way you want to run them. Just a thought...
Good luck, hopefully others will chime in.

[RarlyL8]

O2 bungs are welded into the neck of my mufflers at about 9:30 to 10:00 when looking into the turbine outlet, just a touch over horizontal.
I can reach and install/remove the O2 sensor easily on my units, don't now what you have.

Yes you can trash the Lambda system. Your AFR adjustments will do the job.

[billjam]

Thanks guys, that's useful info.